In recent years, substantial attention has been directed toward the development of golf club heads having desired weight characteristics and, in particular, toward the development of golf club heads having a desired center of gravity location. For example, a designer may want to locate the center of gravity of a golf club head in a predetermined or preferred position relative to the face or "sweet spot" of the golf club head so as to make the golf club head more forgiving upon the occurrence of off-center hits.
Because conventional golf club heads are typically made from metal alloys or other materials having a substantially homogeneous density, the weight characteristics of such golf club heads are typically defined by their overall shape. Thus, to alter the location of the center of gravity of a golf club head, it is often necessary to redesign the shape or configuration of the golf club head. However, this may adversely impact other desired characteristics of the golf club head.
The design process may be further complicated where golf club heads are manufactured using composite materials. Because composite materials are typically less dense than metal and other conventional materials, composite golf club heads generally require additional weighting to achieve desired swing weights for finished golf clubs.
Many solutions have been proposed to adjust and/or increase the weight of composite golf club heads. For example, a weighting agent or material is often introduced into a cavity within a golf club head subsequent to manufacture. In the case of wood type golf club heads, the cavity may be enclosed by the face, sides, sole and crown of the golf club head. However, it is not uncommon for cavities also to be formed, for example, in the sole, heel or toe regions of iron or putter type golf club heads. Because of limited access to the cavities, however, such weighting materials may not be placed as precisely as desired and may not provide the ability to adjust the weight of the golf club heads, or the location of the center of gravity of the golf club heads, very precisely. Furthermore, such materials may dry and separate from the walls of the golf club heads during use, adversely affecting the weight of the golf club heads and possibly creating a distracting sound or feel when the golf clubs are swung.
Alternatively, a composite golf club head may be provided with a metal sole plate or, in the case of wood type golf club heads, a solid or foam core. However, the use of metal sole plates may add undesirable steps in the process of making the golf club heads, and the use of solid or foam core materials has been shown generally to be ineffective for adjusting the location of the center of gravity and moments of inertia of golf club heads. The reason for this is that solid or foam core materials generally have a uniform density, making it difficult to adjust the location of the center of gravity or moments of inertia of the golf club head without simultaneously altering the shape or configuration of the golf club head. Additionally, such materials may result in voids within the golf club head.
For a golf club head including composite material, higher density layers of composite fiber may be provided in the wall of the golf club head to increase its weight. However, such changes in the layers of composite material may affect substantially the structural characteristics of the golf club head.
In view of the foregoing, there appears to be a substantial need for improved methods of manufacturing composite golf club heads and, in particular, for methods that allow for more effective adjustment of the weight characteristics of golf club heads without substantially affecting the structural characteristics of the golf club heads.
There also appears to be a need for improved composite golf club heads manufactured in accordance with such methods.